This application claims the priority of Korean Patent Application No. 10-2003-0060256 filed on Aug. 29, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of Invention
The present invention relates to an apparatus for enhancing a data transfer rate of a multimedia card (MMC), and more particularly, to a method and apparatus for enhancing a data transfer rate by adding a new data transfer channel using a differential signal to a conventional MMC.
2. Description of the Related Art
There have been marketed various types of small-sized terminals conforming to a tendency for all products to be miniaturized with the development of very large scale integrated circuits (VLSIs) and computing techniques. The terminals mentioned herein refer to personal digital assistants (PDAs) and hand held personal computers (HPCs). Accordingly, interface systems that can be connected to such terminals have also gradually decreased in size due to the small sizes of the terminals. In accordance with this tendency, various types of small cards are being developed. Typical of these cards is a multimedia card (hereinafter, simply referred to as “MMC”). First, the MMC will be discussed briefly. Siemens AG and SanDisk Corporation began to develop a new data storage medium called MMC in May of 1997. The MMC is characterized by a small-sized data storage medium, high capacity, applicability to a portable terminal and the like, and efficient use of a battery and an inexpensive and simple interface for a portable terminal.
FIG. 1 is a block diagram showing external appearances and respective terminals of a conventional multimedia card and socket.
A MMC 100 is a memory card having an arrangement of seven terminals: a DAT terminal 16, a CLK terminal 14, a CMD terminal 11, a VDD terminal 13, a VSS terminal 12, a VSS2 terminal 15, and a reserved terminal 10. Further, a MMC socket 110 has a terminal arrangement corresponding to that of the MMC 100.
The DAT terminal 16 is a terminal for transferring a single-ended signal for data, and the CLK terminal 14 is a terminal for receiving a clock (hereinafter, referred to as “MCLK”) for the operation of the MMC from a host controller (120 in FIG. 2). The CMD terminal 11 is a terminal for receiving control commands from the host controller. The control commands include, for example, commands related to control of the MMC, such as data read and data write commands. The VDD terminal 13 is a terminal for applying a DC voltage, and the VSS terminal 12 and the VSS2 terminal 15 are terminals serving as grounds for the DC voltage. The reserved terminal 10 is a reserved terminal prepared such that a user can separately define and use the reserved terminal.
FIG. 2 is a block diagram showing a configuration for transmitting/receiving data between conventional multimedia cards and a host controller.
The host controller 120 is a controller for the MMCs, which recognizes n MMCs 100 and manages control command transfer, data transfer, and the like.
When the host controller 120 sends a relevant command to a MMC 100 via a CMD line 2, the MMC 100 that has received the command sends a relevant response via the CMD line 2. After the relevant control process mentioned above has been performed via the CMD line 2, relevant data are transmitted and received between the host controller 120 and the MMC 100 via a DAT line 7.
That is, the DAT line 7 is used when the conventional MMC 100 transmits and receives data to and from the host 120. At this time, the data are transferred by means of a single-ended signal, i.e. a signal sent in a serial manner via a single line. Since the transfer rate of such a case is theoretically limited to several tens of Mbps (the current limit of the transfer rate is about 50 Mbps), it is difficult to use a conventional MMC for high-speed transfer greater than 100 Mbps.